Cigarettes maker British American Tobacco was the heaviest faller after trading without the right to its latest dividend. Irish building materials group CRH and banking giant Standard Chartered were also declining after going ex-dividend.Meanwhile, car insurance giant Admiral soared in to top spot after it decided to pay a special dividend as it seeks to curb the number of high value bodily injury claims which have dented recent figures. Admiral saw pre-tax profits rise 13% to £299m in 2011 with net revenue up 36% at £870.3m. Both those figures beat the consensus forecast of £291m and £849m, respectively. Antofagasta shares plunged after its Chief Executive Officer, Marcelo Awad, resigned from his position with immediate effect. The mining firm said that until a successor is appointed, Chairman Jean-Paul Luksic will assume the CEO responsibilities on an interim basis. RBS was another big faller, as investors continue to be uneasy over calls by Business Secretary Vince Cable for the bank to be split up. Today Sir George Mathewson, the bank's former Chief Executive, said that it would be 'totally inappropriate' to break up the bank."I do think that to break up the major provider of funds to our existing small businesses is not the correct way to react to this issue [...] I think we should all work harder at getting the relationship correct between bankers and the customers," he said. FTSE 100 - RisersAdmiral Group (ADM) 1,143.00p +9.90%Essar Energy (ESSR) 105.90p +4.23%Evraz (EVR) 393.50p +3.55%Amec (AMEC) 1,107.00p +2.59%Aggreko (AGK) 2,174.00p +2.31%ICAP (IAP) 389.00p +2.21%Petrofac Ltd. (PFC) 1,579.00p +2.20%Burberry Group (BRBY) 1,423.00p +2.15%Compass Group (CPG) 646.00p +2.13%Intertek Group (ITRK) 2,310.00p +2.12%FTSE 100 - FallersBritish American Tobacco (BATS) 3,112.00p -2.49%CRH (CRH) 1,254.00p -2.41%Fresnillo (FRES) 1,791.00p -2.13%Antofagasta (ANTO) 1,217.00p -1.62%Standard Chartered (STAN) 1,541.00p -1.53%Cairn Energy (CNE) 316.50p -1.40%Royal Bank of Scotland Group (RBS) 25.81p -1.38%Barclays (BARC) 236.55p -0.98%Glencore International (GLEN) 398.10p -0.80%Xstrata (XTA) 1,117.00p -0.76%NR